A semiconductor laser module is known which includes a combination of a laser diode and an optical fiber having a grating part provided therein for stabilizing the wavelength of a laser output (See document 1 as an example).
Also, a technique is known for using a wavelength converter to carry out an action of wavelength conversion from a laser beam of which the wavelength has been fixed by a grating part to harmonics (See document 2 as an example).
Moreover, a technique is known for having a wavelength converter beveled at the incident end for attenuating the return of light transmitted back from a wavelength converter towards a laser source (See document 3 as an example).
Document 1
Japanese Patent No. 3120828
Document 2
Japanese Patent No. 3223648
Document 3
Japanese Patent Laid-open Publication (Heisei) 5-93931
(Problems that the Invention is to Solve)
It is probable that the return of light transmitted back from a wavelength converter towards a laser source may make the output of light unstable. One of the prior arts is designed for attenuating the return of light with the use of a wavelength converter beveled at the incident end.
However, when the wavelength converter is beveled at the incident end, its coupling efficiency with the laser source will be declined hence lowering the energy of light output. In addition, the beveling of the incident end of the wavelength converter may be a troublesome task.
It is hence an object of the present invention to provide a solid laser apparatus which is arranged simple in the construction for making the output of harmonic light stable.